I'm setting one up on my mom's 125 right now (more details on that to come) and I'm in the middle of filling it w/ media. I got 5L of Ehfimech and 15L Ehfisubstrat. Well, turns out that's more than I need if I follow the instructions w/ the filter (and the place I got it from also said to add 5L of ehfifix to the top). So, I come to my questions. Do I need the lattice screen on the bottom? That pretty much addresses my 2 concerns about putting media under the lattice screen and making more room. Thanks!